Are Onions and Garlic Healthy? Here’s What Experts Say

Garlic and onions are staples for many home cooks. But do these plants actually add any health benefits to your dishes? Or are they purely for flavor?

People who try to eat colorful fruits and vegetables in order to get a wide range of vitamins and minerals may think that pale foods like onions and garlic don’t offer many nutrients. But although they may not look like nutritional powerhouses, experts say they are.

Onions of all colors (including white) are good sources of vitamin C, vitamin B6, potassium and folate, while garlic is rich in vitamin C, vitamin B6, thiamin, potassium, calcium, phosphorous, copper and manganese. Plus, onions and garlic are a low-calorie way to add flavor to a dish without resorting to ingredients like butter and salt, says Jessica Jones, a California-based registered dietitian.

“Incorporating some garlic and onions into your everyday cooking routine is not only going to be good for the health properties they contain, but it’s also going to make your meals more tasty and hopefully get you more excited about eating nutritious food,” Jones says.

Garlic and onions — which are part of the allium family, along with shallots, leeks and chives — have so many health properties that they are often considered medicinal foods, especially in healing traditions like Ayurveda.

Allium vegetables are rich in organosulfur compounds, which preliminary research suggests may be beneficial for lowering cholesterol and blood pressure and helping to prevent chronic conditions including cancer and cardiovascular disease. But it’s not clear how well the body actually uses these compounds after consumption, especially if the foods are cooked before eating. Some research suggests that raw garlic may provide the most health benefits, so some scientists recommend letting raw crushed or chopped garlic stand for at least 10 minutes before cooking, to allow enzyme-catalyzed reactions to occur before preparation.

Allium vegetables also contain phytochemicals, or chemical compounds in plants that can influence bodily processes. Research suggests that phytochemicals, including those in allium vegetables, may improve immune health and reduce the risk of developing cancer by preventing inflammation, cell damage and DNA damage, according to the American Institute of Cancer Research. Studies have also suggested that garlic and onions have anti-bacterial and anti-viral properties.

What’s clear is that allium vegetables are generally good for gut health. That’s because they contain prebiotics: compounds that feed the microorganisms in fermented foods (otherwise known as probiotics) and “help maintain a healthy gut biome,” says Cara Harbstreet, a Kansas City-based registered dietitian. A 2018 research review found that prebiotic fiber, like that in garlic and onions, may be even better for your gut than the fiber in some fruits, vegetables and whole grains.

One important caveat, however, is that onions and garlic are high in FODMAPs. These are short-chain carbohydrates like sugars and fibers that are, for some people, poorly absorbed by the small intestine. Eating lots of them can cause gastrointestinal distress for people with sensitive GI tracts or conditions like irritable bowel syndrome and acid reflux, resulting in symptoms like gas, bloating, diarrhea and constipation, Jones says. Even garlic and onion powder may cause these reactions.

If you notice gastrointestinal discomfort after eating onions or garlic, it may be worth consulting a registered dietitian to see if FODMAPs are the problem, Harbstreet says. For people who don’t tolerate allium vegetables well, Jones recommends getting a flavor boost from things like garlic-infused olive oil.

Otherwise, there’s no reason to limit your consumption — at least nutritionally speaking. “It adds a lot of flavor to your meals, which can enhance pleasure and satisfaction from your eating experience,” Harbstreet says. “If you’re not rushing into a work meeting or sitting very close to someone else, there’s really no reason to temper your intake.”